Obstructive Sleep Apnea and Heart Rate Variability in Male Patients with Metabolic Syndrome: Cross-Sectional Study

Abstract Background: Obstructive sleep apnea (OSA) is often accompanied by the metabolic syndrome. Because both conditions are associated with depressed heart rate variability (HRV) separately, our aim was to study whether co-morbid OSA is associated with more reduced HRV in male patients with the metabolic syndrome. Methods: In this cross-sectional study, 35 men (age, 57±11 years) with the metabolic syndrome (according to International Diabetes Federation criteria) were included. OSA severity was defined by the apnea–hypopnea index (AHI). HRV was assessed by 24-hr ambulatory electrocardiographic monitoring. Standard deviation of all normal-to-normal RR intervals (SDNN), the high frequency power (HFP), and the ratio of low- to high-frequency power (LF/HF) were measured. Results: There were 14, 6, and 8 cases of severe (AHI ≥30/hr), moderate (15/hr≤AHI <30/hr), and mild (5/hr ≤AHI <15/hr) OSA, respectively. Seven patients had no OSA. Patients with mild–moderate or severe OSA had reduced SDNN and HFP values...